Photovoltaic cells convert radiation, for example visible light, into direct current (DC) electricity. Organic solar cells (OSC) are organic photoelectric conversion devices which comprise conductive organic polymers or organic small molecules, for light absorption, charge generation and charge transport. Organic dye compounds find use in many applications, including solar panels and photodetectors. They may also be part of larger systems comprising other organic electronic devices, such as organic light emitting diodes (OLEDs) and organic thin film transistors (OTFTs).
A common small-molecule OSC structure is formed by a transparent conducting oxide (TCO) electrode, typically Indium Tin Oxide (ITO), an organic hole collecting layer (for example the doped polymer PEDOT:PSS), a photoactive layer, and the metallic contact, in some cases a thin interlayer of calcium or lithium fluoride. The photoactive layer is formed from a blend of donor and acceptor organic semiconductors. Typically, the acceptor semiconductor is a soluble fullerene derivative and the donor semiconductor is a small-molecule organic dye compound.
Suitable dye compounds for small-molecule OSCs have been reported in the literature, e.g. in Fitzner, R et al., Journal of the American Chemical Society, 2012, 134, 11064-11067, which is incorporated herein fully by reference. However, there is still a need for dye compounds for OSCs with improved properties.